Joseph Bergin
berginf@pace.edu
The following nine patterns form a pattern language.
The above patterns work well together as indicated within each pattern. Actually these arose over many years of teaching. It is object-orientation, however, in which they find their greatest manifestation yet.Back in the late 1970's when U.S. educators were moving from Fortran to Pascal we made a number of serious errors early on. Many of the books of the time were better as reference works than as texts for students. Most of the early books relegated functions to a very late chapter. Types weren't used especially well and ADT's were non-existent.
I remember what a revelation it was to find the book Karel the Robot, by Richard Pattis. Here were functions done first, not just early. Here was a very simple starter that showed the Lay of the Land of programming. It was simultaneously a Toy Box and the first cycle of a Spiral. Very powerful stuff, and very useful for both educators and students. The algorithms developed with Karel had direct impact on learning Pascal. For example, a robot searching for a beeper has exactly the same structure as a program searching a sentence for its period.
I fear we are making the same errors in moving from procedural programming to object-orientation. I've read papers lately, written by educators, who claim that the "received wisdom" is that object-orientation should be taught late, as an add on to procedural programming. This goes counter to the experience of professionals in the object-oriented world who have seen how much differently one must think to be successful in this new world. If you want to produce object-oriented developers, they should learn this first (Early Bird).
The field is complex and has many parts. These must be shown to fit together in comprehensible ways (Lay of the Land). The programs we build now are much larger and more complex than was true ten years ago. Students need to be introduced to this scale (Toy Box). Reuse is more important now (Tool Box). Languages are more complex (Test Tube, Mistake).
Software is built in teams, and maintenance is often the dominant cost. Programs are too big to be understood by individuals and they grow from a well-designed core (Larger than Life, Fixer Upper).
We are teaching new and better topics and tools than we did a few years ago. I believe that our methodology must change as well. When teaching Pascal, few relied on pre built libraries of code with which the students would interact, since most Pascal programs are built largely from scratch. Most C++ and Java programs are not built that way, however, so students need different experience than many of their instructors had. This implies that the instructor must be prepared, not only with knowledge and pedagogy, but with tools and libraries. It took me 25 years to know what I do about computer science. I expect my students to get there in less than a third of that time. Their experiences need to be very different from mine to make this possible.
In fact, object-orientation itself can provide these tools. Well designed classes are inherently reusable. They can be used to build toys which give the students both examples of object-orientation that they can emulate, but also tools to work with and extend. We must learn to use the tools to teach the tools. And we must match our pedagogy to the exciting new things that we are trying to teach.
Note: One of the themes that run through all of these patterns is the requirement that the artifacts that we show students be of the highest quality. Programs must be beautiful as well as correct. Designs must be excellent. Our programming and diagramming style must be of the highest order. Students look up to professors for guidance and emulate what we do. It is occasionally ok to show students work in development, but they should also see the final products. Perhaps I should have written this as a pattern (Quality is Job One).
| Back |